| In the relational database model, data can be visualized as being stored in a number of tables, where each table represents a relation. Columns in the table are attributes of each relation, while the rows in the table consist of tuples that describe each instance of the relation.
The relation schema is defined as R(A1, A2...An) where R is the name of the relation and each attribute Ai is the role a domain (for example, the set of all 9-digit integers as a domain for social security number) plays in the relation. The degree of R is the number of attributes in its schema.
An instance, or relation state of a relation, r(R) consists of a set of n-tuples r{t1, t2, .... , tn}.
Tables in the relational database model are manipulated through relational algebra. | 
